i2c: pca954x: Add option to skip disabling PCA954x Mux device

On some Layerscape boards like LS2085ARDB/LS2080ARDB,
input pull-up resistors on PCA954x Mux device are
missing on board. So, if mux are disabled after powered-on,
input lines will float leading to incorrect functionality.

Hence, PCA954x Mux device should never be turned-off after
power-on.

Add option to skip disabling PCA954x Mux device
if device tree contians "i2c-mux-never-disable" property
for pca954x device node.

Signed-off-by: Zhang Ying-22455 <ying.zhang22455@nxp.com>

1 files changed, 43 insertions, 0 deletions

diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c
index 9c4ac26..3c27ab8 100644
--- a/drivers/i2c/muxes/i2c-mux-pca954x.c
+++ b/drivers/i2c/muxes/i2c-mux-pca954x.c
@@ -74,6 +74,7 @@ struct pca954x {
 	u8 last_chan;		/* last register value */
 	u8 deselect;
 	struct i2c_client *client;
+	u8 disable_mux;		/* do not disable mux if val not 0 */
 };
 
 /* Provide specs for the PCA954x types we know about */
@@ -196,6 +197,13 @@ static int pca954x_deselect_mux(struct i2c_mux_core *muxc, u32 chan)
 	if (!(data->deselect & (1 << chan)))
 		return 0;
 
+#ifdef CONFIG_ARCH_LAYERSCAPE
+	if (data->disable_mux != 0)
+		data->last_chan = data->chip->nchans;
+	else
+		data->last_chan = 0;
+	return pca954x_reg_write(muxc->parent, client, data->disable_mux);
+#endif
 	/* Deselect active channel */
 	data->last_chan = 0;
 	return pca954x_reg_write(muxc->parent, client, data->last_chan);
@@ -228,6 +236,28 @@ static int pca954x_probe(struct i2c_client *client,
 		return -ENOMEM;
 	data = i2c_mux_priv(muxc);
 
+#ifdef CONFIG_ARCH_LAYERSCAPE
+	/* The point here is that you must not disable a mux if there
+	 * are no pullups on the input or you mess up the I2C. This
+	 * needs to be put into the DTS really as the kernel cannot
+	 * know this otherwise.
+	 */
+	match = of_match_device(of_match_ptr(pca954x_of_match), &client->dev);
+	if (match)
+		data->chip = of_device_get_match_data(&client->dev);
+	else
+		data->chip = &chips[id->driver_data];
+
+	data->disable_mux = of_node &&
+		of_property_read_bool(of_node, "i2c-mux-never-disable") &&
+		data->chip->muxtype == pca954x_ismux ?
+		data->chip->enable : 0;
+	/* force the first selection */
+	if (data->disable_mux != 0)
+		data->last_chan = data->chip->nchans;
+	else
+		data->last_chan = 0;
+#endif
 	i2c_set_clientdata(client, muxc);
 	data->client = client;
 
@@ -240,11 +270,16 @@ static int pca954x_probe(struct i2c_client *client,
 	 * that the mux is in fact present. This also
 	 * initializes the mux to disconnected state.
 	 */
+#ifdef CONFIG_ARCH_LAYERSCAPE
+	if (i2c_smbus_write_byte(client, data->disable_mux) < 0) {
+#else
 	if (i2c_smbus_write_byte(client, 0) < 0) {
+#endif
 		dev_warn(&client->dev, "probe failed\n");
 		return -ENODEV;
 	}
 
+#ifndef CONFIG_ARCH_LAYERSCAPE
 	match = of_match_device(of_match_ptr(pca954x_of_match), &client->dev);
 	if (match)
 		data->chip = of_device_get_match_data(&client->dev);
@@ -252,6 +287,7 @@ static int pca954x_probe(struct i2c_client *client,
 		data->chip = &chips[id->driver_data];
 
 	data->last_chan = 0;		   /* force the first selection */
+#endif
 
 	idle_disconnect_dt = of_node &&
 		of_property_read_bool(of_node, "i2c-mux-idle-disconnect");
@@ -312,6 +348,13 @@ static int pca954x_resume(struct device *dev)
 	struct i2c_mux_core *muxc = i2c_get_clientdata(client);
 	struct pca954x *data = i2c_mux_priv(muxc);
 
+#ifdef CONFIG_ARCH_LAYERSCAPE
+	if (data->disable_mux != 0)
+		data->last_chan = data->chip->nchans;
+	else
+		data->last_chan = 0;
+	return i2c_smbus_write_byte(client, data->disable_mux);
+#endif
 	data->last_chan = 0;
 	return i2c_smbus_write_byte(client, 0);
 }